Internet of Things (IoT) devices and technology are increasingly being integrated into smart grids. These devices come with a lot of security vulnerabilities. To combat this, IoT protocols have been extended with security mechanisms. However, these mechanisms introduce extra processing that can lead to additional delay. This additional delay can affect the reliable operation of a smart power system which depends on prompt communication. This paper investigates the real time properties of IoT communication security protocols. We determine the impact of IoT protocols on the real time requirements of smart grid functions (protection, control, and monitoring). We measure how much communication traffic size and delay are added and how it scales. We determine the requirements that must be met by the optimized security protocols. Three IoT communication protocols were considered: CoAP/DTLS, MQTT/TLS, and XMPP/TLS. Results show both latency and overhead increased by a minimum of for each protocol. The increase in delay was below the recommended maximum standard for microgrid monitoring but exceeded the recommended standard for control operations.